A mounting panel for securing heating medium ducting in floors is known from German Patent specification No. 1,929,529, made of a base plate with planar parallel sides, with cylindrical projections arranged on one side, between which the heating medium ducting can be secured (DT-AS No. 1,929,529). These mounting panels are laid in a building on a supporting base made of concrete, wood or the like, or on an insulating layer. Heating medium ducting which is connected at its ends to the flow and return of a central heating system is inserted according to a specific layout between the projections and is held in place by them. Steel plates are laid on the projections. These form the floor which is actually walked on. In the known mounting panel the cylindrical projections have a uniform diameter. This diameter is determined by two factors, which determine the maximum and minimum diameters which can be used. From the point of view of high load-bearing capacity and in order to give a substantial support for the structural panels (typically steel plates) laid thereon, the projections should have a large diameter. Only then will the steel plates be adequately supported and, particularly with point loading, be prevented from bending down in between the individual projections and rising up along their edges. However, projections with a large diameter restrict the free laying of the heating medium ducting. The space occupied by large diameter projections is no longer available for the ducting. This does not affect so much the straight runs of ducting as it does loops and return bends. At points where the ducting reverses its laying direction, it should follow the widest possible curve. In the known mounting panel a compromise has therefore to be made in establishing the diameter of the projections. This means that either the supporting of the steel plates or the possibility of laying the heating ducting freely must suffer.